Document the LPASS (low power audio subsystem) clock controller
found on Qualcomm devices.

Cc: <devicetree@vger.kernel.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Kumar Gala <galak@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Michael Turquette <mturquette@linaro.org>